Multifunctional Memory Research Articles

Ultrafast reconfigurable direct charge trapping devices based on few-layer MoS2

Abstract Charge trapping devices incorporating 2D materials and high-κ dielectrics have emerged as promising candidates for compact, multifunctional memory devices compatible with silicon-based manufacturing processes. However, traditional charge trapping devices encounter bottlenecks including complex device structure and low operation speed. Here, we demonstrate an ultrafast reconfigurable direct charge trapping device utilizing only a 30 nm-thick Al2O3 trapping layer with a MoS2 channel, where charge traps reside within the Al2O3 bulk confirmed by transfer curves with different gate-voltage sweeping rates and photoluminescence (PL) spectra. The direct charging tapping device shows exceptional memory performance in both three-terminal and two-terminal operation modes characterized by ultrafast three-terminal operation speed (≈300 ns), an extremely low OFF current of 10-14 A, a high ON/OFF current ratio of up to 107, and stable retention and endurance properties. Furthermore, the device with a simple symmetrical structure exhibits VD polarity-dependent reverse rectification behavior in the high resistance state (HRS), with a rectification ratio of 105. Additionally, utilizing the synergistic modulation of the conductance of the MoS2 channel by VD and VG, it achieves gate-tunable reverse rectifier and ternary logic capabilities.

Brain‐inspired Multimodal Synaptic Memory via Mechano‐photonic Plasticized Asymmetric Ferroelectric Heterostructure

AbstractNeuromorphic devices capable of emulating biological synaptic behaviors are crucial for implementing brain‐like information processing and computing. Emerging 2D ferroelectric neuromorphic devices provide an effective means of updating synaptic weight aside from conventional electrical/optical modulations. Here, by further synergizing with an energy‐efficient synaptic plasticity strategy, a multimodal mechano‐photonic synaptic memory device based on 2D asymmetric ferroelectric heterostructure is presented, which can be modulated by external mechanical behavior and light illumination. By integrating the asymmetric ferroelectric heterostructured field‐effect transistor and a triboelectric nanogenerator, the mechanical displacement‐derived triboelectric potential is ready for gating, programming, and plasticizing the synaptic device, resulting in superior electrical properties of high on/off ratios (> 107), large storage windows (equivalent to ≈95 V), excellent charge retention capability (> 104 s), good endurance (> 103 cycles), and primary synaptic behaviors. Besides, optical illumination can effectively synergize with mechanoplasticity to implement multimodal spatiotemporally correlated dynamic logic. The demonstrated multimodal memory synapse provides a facile and promising strategy for multifunctional sensory memory, interactive neuromorphic devices, and future brain‐like electronics embodying artificial intelligence.

Observation of Moment-Dependent and Field-Driven Unidirectional Magnetoresistance in CoFeB/InSb/CdTe Heterostructures.

Magnetoresistance effects are crucial for understanding the charge-spin transport as well as propelling the advancement of spintronic applications. Here, we report the coexistence of magnetic-moment-dependent (MD) and magnetic-field-driven (FD) unidirectional magnetoresistance (UMR) effects in CoFeB/InSb/CdTe heterostructures. The strong spin-orbital coupling of InSb and the matched impedance at the CoFeB/InSb interface warrant a distinct MD-UMR effect at room temperature, while the interaction between the in-plane magnetic field and the Rashba effect at the InSb/CdTe interface induces the marked FD-UMR signal that dominates the high-field region. Moreover, owning to different spin scattering mechanisms, these two types of non-reciprocal charge transports show opposite polarities with respect to the magnetic field direction, which further enables an effective phase modulation of the angular-dependent magnetoresistance. The demonstration of the tunable UMR response validates our CoFeB/InSb/CdTe system as a suitable integrated building block for multifunctional spintronic memory and sensor designs.

Preparation, optical properties, room temperature ferromagnetism, and mechanism of ordered nanotube-like tantalum oxide films

Physical property changes caused by defects have recently attracted significant attention due to their potential applications in sensors, spintronic devices, and multifunctional memory. Due to their numerous surface defects, this study fabricated ordered Ta2O5 nanotube (NT) thin films on Ta foil through an anodization technique. Then, the oxygen bubble model was applied to explain the formation of NTs from the perspective of lattice orientation. Furthermore, this study investigated influence of anodization duration and annealing treatment on the crystal structure, optical properties, and magnetic behavior. Notably, room-temperature ferromagnetism was observed in the as-prepared Ta2O5 NTs for the first time. After annealing in an argon atmosphere, the band gap of the sample decreased, accompanied by an increase in ferromagnetism. The underlying mechanism for this phenomenon was elucidated using a hydrogen-like impurity model. Consequently, this study on the magnetism of Ta2O5 NTs holds excellent potential for expanding their application in spin electronic devices.

Tunable magnetic switching behavior in La0.7Sr0.3MnO3/PbTiO3 multilayers

Tuning magnetic switching behavior and related magnetic configuration of transition metal oxides (TMOs) is critical for realizing multifunctional materials and devices. In this study, we manipulated the magnetic switching behavior through interface engineering by introducing ferroelectric PbTiO3 (PTO) to form La0.7Sr0.3MnO3 (LSMO)/PTO multilayers. Both the normal hysteresis loop (NHL) and the inverted hysteresis loop (IHL) could be tuned by changing the PTO thickness. All multilayers displayed a transition from NHL to IHL with increasing temperature, and the transition temperature increased with the insertion of the PTO layer or increasing thickness of the PTO. In addition, it was found that the increase in the Curie temperature (Tc) and saturation magnetization (Ms), as well as the decrease in the coercive field (Hc) and exchange bias field (Heb) with a reduction in the thickness of the PTO, is possibly related to the interface phase. This study illustrates the influence of the ferroelectric PTO thickness on the magnetic switching behavior and related magnetic configuration in LSMO, which is possibly driven by the unscreened depolarization charge and oxygen octahedral tilting. This finding may benefit the application of TMOs in multifunctional memory devices.

Development of an electro-thermo-mechanical 4D printed multi-shape smart actuator: Experiments and simulation

This investigation presents an experimental and numerical approach to developing 4D printed multi-shape actuators with an integrated electrical self-triggering system. It employs a multifunctional shape memory carbon black Polylactic Acid (PLA) layer embedded within rubbery thermoplastic polyurethane (TPU). Notably, these thermo-responsive actuators are programmed and triggered using Joule’s effect, eliminating the need for an external heat source and enabling precise control of temperature gradients. Two distinct motion mechanisms are employed: the differences in thermal expansion coefficient between the PLA/TPU polymers below the glass transition temperature, and the shape memory effect of the PLA layer above the glass transition temperature. As a result, a diverse range of motion responses can be achieved by adjusting the potential differences. A coupled electro-thermo-mechanical finite element model is used to gain further insight into the motion mechanisms, offering predictive capabilities beyond the ones reported by previous models. The developed technology provides enhanced actuation capabilities to conventional bi-shape SMP actuators, offering a versatile range of bending cycles. Furthermore, Joule’s effect enables the implementation of closed-loop control systems, which is essential for developing autonomous robotic systems.

2D Reconfigurable Memory Device Enabled by Defect Engineering for Multifunctional Neuromorphic Computing.

In this era of artificial intelligence and Internet of Things, emerging new computing paradigms such as in-sensor and in-memory computing call for both structurally simple and multifunctional memory devices. Although emerging two-dimensional (2D) memory devices provide promising solutions, the most reported devices either suffer from single functionalities or structural complexity. Here, this work reports a reconfigurable memory device (RMD) based on MoS2/CuInP2S6 heterostructure, which integrates the defect engineering-enabled interlayer defects and the ferroelectric polarization in CuInP2S6, to realize a simplified structure device for all-in-one sensing, memory and computing. The plasma treatment-induced defect engineering of the CuInP2S6 nanosheet effectively increases the interlayer defect density, which significantly enhances the charge-trapping ability in synergy with ferroelectric properties. The reported device not only can serve as a non-volatile electronic memory device, but also can be reconfigured into optoelectronic memory mode or synaptic mode after controlling the ferroelectric polarization states in CuInP2S6. When operated in optoelectronic memory mode, the all-in-one RMD could diagnose ophthalmic disease by segmenting vasculature within biological retinas. On the other hand, operating as an optoelectronic synapse, this work showcases in-sensor reservoir computing for gesture recognition with high energy efficiency.

Enhanced Glycosylation Caused by Overexpression of Rv1002c in a Recombinant BCG Promotes Immune Response and Protects against Mycobacterium tuberculosis Infection.

Tuberculosis (TB) is a major global health threat despite its virtual elimination in developed countries. Issues such as drug accessibility, emergence of multidrug-resistant strains, and limitations of the current BCG vaccine highlight the urgent need for more effective TB control measures. This study constructed BCG strains overexpressing Rv1002c and found that the rBCG-Rv1002c strain secreted more glycosylated proteins, significantly enhancing macrophage activation and immune protection against Mycobacterium tuberculosis (M. tb). These results indicate that Rv1002c overexpression promotes elevated levels of O-glycosylation in BCG bacteriophages, enhancing their phagocytic and antigenic presentation functions. Moreover, rBCG-Rv1002c significantly upregulated immune regulatory molecules on the macrophage surface, activated the NF-κB pathway, and facilitated the release of large amounts of NO and H2O2, thereby enhancing bacterial control. In mice, rBCG-Rv1002c immunization induced greater innate and adaptive immune responses, including increased production of multifunctional and long-term memory T cells. Furthermore, rBCG-Rv1002c-immunized mice exhibited reduced lung bacterial load and histological damage upon M. tb infection. This result shows that it has the potential to be an excellent candidate for a preventive vaccine against TB.

Reversible near-infrared light-induced spin-state transition on layered Co-MOF

The spin-crossover (SCO) can be triggered by light or pressure changes, making it a promising system for multifunctional switches and memory devices at the molecular level. In this work, we have reported a NIR-responsive spin state switching system via doping layered Co(pyridine)2Ni(CN)4 (Co-MOF) into the stable polyvinylidene fluoride matrix for the first time. The layered Co-MOF has shown a rapid response of color change between gray-white and blue, which could be attributed to the SCO behavior triggered by NIR illumination. The new system ensures the soft network structures of the matrix to facilitate the homogeneous distribution of layered Co-MOF, both of which contribute to outstanding reversibility performance, including fast response, coloration in a short period, and decoloration in the ambient environment. This work provides a viable strategy to construct a new NIR-triggered SCO system for molecular switches and spintronic devices.

Colossal Magnetoresistive Switching Induced by d0 Ferromagnetism of MgO in a Semiconductor Nanochannel Device with Ferromagnetic Fe/MgO Electrodes.

Exploring potential spintronic functionalities in resistive switching (RS) devices is of great interest for creating new applications, such as multifunctional resistive random-access memory and novel neuromorphic computing devices. In particular, the importance of the spin-triplet state of cation vacancies in oxide materials, which is induced by localized and strong O-2p on-site Coulomb interactions, in RS devices has been overlooked. d0 ferromagnetism sometimes appears due to the spin-triplet state and ferromagnetic Zener's double exchange interactions between cation vacancies, which are occasionally strong enough to make nonmagnetic oxides ferromagnetic. Here, for the first time, anomalous and colossal magneto-RS (CMRS) with very high magnetic field dependence is demonstrated by utilizing an unconventional RS device composed of a Ge nanochannel with all-epitaxial single-crystalline Fe/MgO electrodes. The device shows colossal and unusual behavior as the threshold voltage and ON/OFF ratio strongly depend on a magnetic field, which is controllable with an applied voltage. This new phenomenon is attributed to the formation of d0 -ferromagnetic filaments by attractive Mg vacancies due to the spin-triplet states with ferromagnetic double exchange interactions and the ferromagnetic proximity effect of Fe on MgO. The findings will allow the development of energy-efficient CMRS devices with multifield susceptibility.

Identification and relative abundance of naturally presented and cross-reactive influenza A virus MHC class I-restricted T cell epitopes

ABSTRACT Cytotoxic T lymphocytes are key for controlling viral infection. Unravelling CD8+ T cell-mediated immunity to distinct influenza virus strains and subtypes across prominent HLA types is relevant for combating seasonal infections and emerging new variants. Using an immunopeptidomics approach, naturally presented influenza A virus-derived ligands restricted to HLA-A*24:02, HLA-A*68:01, HLA-B*07:02, and HLA-B*51:01 molecules were identified. Functional characterization revealed multifunctional memory CD8+ T cell responses for nine out of sixteen peptides. Peptide presentation kinetics was optimal around 12 h post infection and presentation of immunodominant epitopes shortly after infection was not always persistent. Assessment of immunogenic epitopes revealed that they are highly conserved across the major zoonotic reservoirs and may contain a single substitution in the vicinity of the anchor residues. These findings demonstrate how the identified epitopes promote T cell pools, possibly cross-protective in individuals and can be potential targets for vaccination.

A covalent organic polymer-based transistor with multifunctional memory and synaptic functions

An organic synaptic transistor was fabricated with a covalent organic polymer MT-TP to mimic the behavior of biological synapses.

Experimental demonstration and analysis of crossbar array memristor for brain-inspired computing

The human brain accomplishes intricate computational tasks like learning, recognition, and cognition with minimal power usage, and showcases synaptic behavior well-suited for neuromorphic computing systems. The latest advancements in memristive devices are pivotal for designing memory and synapses, as well as for non-volatile data storage and computing. However, a directive on realizing memristive analog behavior is still a major concern. Here we propose forming free digital and analog resistive switching (ARS) dynamics of 4 × 4 crossbar array MgZnO-based memristive devices for neural activity (Potentiation/Depression). Moreover, our device demonstrates both abrupt and gradual resistive switching (RS) behaviors, with acceptable endurance (10 K cycles at 85 °C), data retention (107 s), a read voltage range of 0.1 V to 0.5 V, and pulse widths ranging from 50 μs to 250 μs (with a pulse interval of 50 μs) for synaptic behavior for neuromorphic computing. Our approach deals with multifunctional memory and synaptic behavior with low voltage linearity and excellent switching characteristics. Our results highlight the potential of memristor for energy-efficient edge computing and brain-inspired computing systems.

Recent Advances in Shape Memory Polymers: Multifunctional Materials, Multiscale Structures, and Applications

AbstractShape memory polymers (SMPs) are one of the primary directions in the development of modern high‐tech new materials, which are integrated with sensing, actuation, information processing, and autonomous deformation. Here, multifunctional shape memory polymers are focused and a detailed introduction to the characteristics of self‐deformation, self‐sensing, self‐healing, and self‐learning is provided. Integrating with other functional materials to form shape memory polymer composites (SMPC), designing and controlling the material structure and organization at the microscale, thereby achieving more precise and controllable shape memory effects and expanding the potential of material applications. Ultimately, it is shown that SMPs and their composites have a wide range of fascinating applications in the fields of robotics, smart clothing, smart textiles, biomedical devices, and wearable technology. SMPs will thus continue to play a significant role in future deeper exploration.

A 2D Heterostructure-Based Multifunctional Floating Gate Memory Device for Multimodal Reservoir Computing.

The demand for economical and efficient data processing has led to a surge of interest in neuromorphic computing based on emerging two-dimensional (2D) materials in recent years. As a rising van der Waals (vdW) p-type Weyl semiconductor with many intriguing properties, tellurium (Te) has been widely used in advanced electronics/optoelectronics. However, its application in floating gate (FG) memory devices for information processing has never been explored. Herein, an electronic/optoelectronic FG memory device enabled by Te-based 2D vdW heterostructure for multimodal reservoir computing (RC) is reported. When subjected to intense electrical/optical stimuli, the device exhibits impressive nonvolatile electronic memory behaviors including ≈108 extinction ratio, ≈100 ns switching speed, >4000 cycles, >4000-s retention stability, and nonvolatile multibit optoelectronic programmable characteristics. When the input stimuli weaken, the nonvolatile memory degrades into volatile memory. Leveraging these rich nonlinear dynamics, a multimodal RC system with high recognition accuracy of 90.77% for event-type multimodal handwritten digit-recognition is demonstrated.

Material-enabled damage inspection of multifunctional shape memory alloy tufted composite T-joints

The through-the-thickness reinforcement of carbon-epoxy composite joints with shape memory alloy (SMA) tufts has shown significant improvement of the mechanical strength, fracture toughness, and delamination resistance. This study explores the thermal-electric properties of SMA filaments tufted in composite T-joints to exhibit multiple functionalities including material-enabled thermographic inspection and structural health monitoring via in-situ strain sensing. Infrared thermography image analysis was performed on both pristine and damaged T-joint specimens subject to pull-off testing. Experimental results showed that the heat generated by SMA tufts measured by an infrared camera provided accurate indication of delamination perpendicular to the tuft direction. SMA tufts were also used as strain sensors embedded within the T-joint. Local changes of the electrical resistance in SMA filaments, both separately and within the joint, were observed during pulling loads. Digital Image Correlation measurements exhibited good correlation between electrical resistance variations and the opening of delamination. These results pave the way for the development of multifunctional composite joining systems combining enhanced through-the-thickness damage tolerance and self-sensing capabilities.

Insight of the high switching window and data retention in lead-free 2D layered double perovskite resistive memory device

Lead-free robust halides double perovskites (DPs) are evolving as the key materials for the multi-functional resistive memory application. Herein, we aimed to enhance the switching window, i.e., current On/Off ratio by the cutting edge dimensional reduction of the three dimensional Cs2AgBiBr6 DP into two dimensional (2D) BA4AgBiBr8 (BA = butylammonium) DP and studied the insight of their resistive switching anomaly. We affirmed that the improved On/Off ratio (∼103 to ∼106) is attributed to the restricted charge transport in the high resistance state (HRS) of the BA4AgBiBr8 based switching device. The low HRS current can be ascribed to the synergies of higher Schottky barrier at the Au/BA4AgBiBr8 junction and higher thermal activation energy in the layered DP. Owing to the higher switching window in the 2D DP device, reproducible endurance (tested up to 500 cycles) and retentivity (tested up to 104 s) of the resistance states establish that the high On/Off ratio could be retained without significant deviation. The resistive memory behavior could be hypothesized by the charge trapping phenomenon in the BA4AgBiBr8 DP, as the charge retention was persisted over 60 min as evident from surface potential images of Kelvin probe force microscopy.

Donor-acceptor hyperbranched copolyimides contain different linear segment for electrochromic and resistive memory devices

In this work, two hyperbranched copolyimides (O-coPI and F-coPI) were synthesized which the diamine donors in the linear segment contain different substituents. To investigate the effects of substituents in donors on their memory behavior, the corresponding linear polyimides (F-LPI and O-LPI) were also discussed. The devices based on hyperbranched copolyimides exhibited non-volatile write once read many times memory (WORM) behavior, while the devices based on linear polyimides exhibited volatile memory dynamic random-access memory (DRAM) behavior. Polyimides (O-coPI and O-LPI) prepared with methoxy-substituted diamine donors have low switching voltages due to their good electron-donating properties. In addition, O-coPI and O-LPI also exhibit electrochromic properties. Hyperbranched copolyimide O-coPI have higher optical contrast and faster response time than that of linear polyimide O-LPI. This work provides a new direction for the development of multifunctional memory materials.

4D printing of shape memory polymer nanocomposites for enhanced performances and tunable response behavior

The emergence of four-dimensional (4D) printing introduces a novel approach to the design and manufacturing of high-performance multifunctional shape memory polymers (SMPs). Herein, two types of nanomaterials were blended or embedded into SMPs matrix to enable 4D printing of shape memory polymer composites (SMPCs) via photocuring. The incorporation of hexagonal boron nitride (HBN) nanoparticles enhanced the thermal stability and mechanical properties of SMPs, and accelerated their thermally responsive shape recovery speed. HBN nanoparticles also significantly improved the performance stability of SMPs, even after undergoing multiple shape memory cycles. Electrically responsive shape memory behavior in SMPCs was achieved by embedding a spray-coated polyaniline: polystyrene sulfonate /graphene (PANI: PSS/GR) electrothermal layer (ETL). The applied voltage, ETL resistance, HBN blend content, and sample thickness had a significant regulation effect on electrically responsive shape recovery behavior and shape recovery force. PANI: PSS improved adhesion between ETL and SMPCs matrix, filled the gaps between graphene platelets, which resulted in rapid, uniform, and stable heating upon energization. The presented electrically responsive gripper was capable of grasping objects of various shapes and sizes. This strategy broadens the potential applications of 4D printed SMPCs in challenging environments while propelling the advancement of 4D printing.

2D Heterostructures Induced Charge Transfer and Trapping for Hybrid Optically and Electrically Controllable Nonvolatile Memory

AbstractNonvolatile memory is an indispensable component of electronic devices. However, the current technology makes it difficult to satisfy the emerging big data demand. To circumvent the existing problems, herein, a first attempt is made to achieve multifunctional nonvolatile memory based on all 2D heterostructures, consisting of histidine‐doped molybdenum disulfide quantum disks mixed with graphene oxide and a graphene macroscopic heterojunction. The designed device possesses intriguing hybrid electrically and optically controllable nonvolatile memory functionalities. By harnessing the unique properties of these materials, memory devices demonstrate long‐term stability and nonvolatile characteristics under both optical and electrical control signals. These devices possess outstanding features, such as multiple read‐write cycles, multi levels, and fast switching speeds, overcoming the limitations of traditional components. To explore the underlying physical mechanism, the Fermi level of graphene is measured and it is confirmed that the charge transfer and trapping across the heterojunctions are the major factors responsible for the observed behavior. This study demonstrates that 2D heterostructures for hybrid optically and electrically controllable nonvolatile memory pave an alternative route for the next‐generation information technology.